Yogi bear could learn a thing or two from Christopher Knight: the 47-year-old hermit has apparently been living in the woods of Maine for 27 years – surviving by stealing food and supplies from local campsites.

When he was finally caught by a game warden who set up a surveillance alarm he told police he had not spoken to another person since the 90s.

He survived in a tent covered by tarpaulin, with a stove and and a bed, and was called the "North pond hermit" by local people.

Survivalist Guy Grieve, who lived for a year in the wilderness of Alaska, says the large canvas tent with tarpaulin would have kept Knight warm – especially if he had a wood-burning stove inside. "When it snows you dig the snow round the tent and bury it, but if I didn't want to be found I would have found a cave."

But Grieve says he was not surprised the hermit chose to steal food. "He could hunt and fish and trap, but I suppose like any other wild animal he saw the convenience in campsites."

Forager John Wright agrees. "Woods are quite hard to live in. You could get a large stock of mushrooms, but they aren't around for very long.

"There are a lot of edible leaves, such as nettles or watercress – but you would have to eat a lot of them and you have to know what you are doing. And he may have had access to fish. There are a lot of edible water plants, but you would have to know what you are doing.

"There may also be some fruit, and you could cook acorns, but you would need to boil them for about eight hours. What you really need is carbohydrates, which you could get from roots – but it would be pretty poor fare, pretty ghastly."

The biggest problem the hermit would have faced, say both men, is having no one to learn from.

"You can learn by trial and error," says Wright, "but you only get one error. In the UK, for instance, the roots that are the most plentiful and tasty-looking are hemlock water dropwort – they look like carrots and they have lots of carbohydrates, but they also have a deadly liver toxin and can kill you in three hours. I don't know how he would survive long enough to learn."

Grieve agrees. "If you live in the wilderness you realise we need each other. When I arrived I had this idea of 'one man in the wilderness, finding himself' – but the moment I got out there I was shrunk and intimidated by it all. I made so many mistakes and had so many disasters I realised I had to learn. The people I met in Alaska taught me how to live.

"When it worked properly in the wilderness was when I was with my family – the family unit is the best to cope with the wilderness.